The general area of the present invention is electrical connection and the specific area is electrical connection through forced contact of conductors within flexible, flat, printed strip conductor cable with corresponding printed circuit (pc) conducting lands on a printed circuit board or glass substrate.
Prior art connectors have been developed to provide low-cost Zero Insertion Force (ZIF) connectors to terminate flat printed conductor cable of flexible and conductive ink circuitry on pc boards or glass substrates. An example is the ZIF connector design development of AMP, Inc., Harrisburg,
17105, manufactured under the tradename "Connector Clip" and reviewed in the Dec. 17, 1979 issue of Design News, at page 70. Similarly to the present invention, the low-resistance electrical connections are obtained from direct, spring-forced contact between the plated surfaces of the cable conductors and the circuit strips of the board or plate. This prior art connector has only one component part and this part, a stainless steel stamping, has no electrical or insulating function.
This prior art stamping is claimed to provide a number of different mechanical functions. These include the anchoring of its own body to the printed circuit board or glass plate; the development of high normal forces required to reliable, low-resistance electrical connection; provision for relieving these spring-developed forces during Zero Insertion Force (ZIF) cable insertion and removal; prevention of overstressing of these springs during the ZIF operations; and positive positioning, locking, and strain relief of the cable. These various functions are produced by a simple design geometry. The stamping is produced by high-speed, progressive-die precision stamping techniques at low cost with negligible part-to-part variation in performance.
A second prior art connector is shown in U.S. Pat. No. 4,265,507 to D. L. Johnson for an Electrical Connector for Strip Conductors. This connector utilizes a U-channel shaped shell to clamp a multiple strip flat flexible conductor cable at the edge of a body member or substrate. The connector is claimed to support zero insertion forces and reliable positive connection in the face of environmental variation such as temperature, vibration and shock.
The present invention will be seen to endorse the concept of AMP and Johnson to utilize spring force to effectuate electrical connection to multiple strip conductors within a flexible flat cable. The present invention also endorses the Johnson concept that the conductor cable should be fixedly held at the edge of the substrate body by the clamping shell and that the shell itself should be fixedly held in position by securing means such as extending projections adapted to engage the connector shell. The present invention will be seen to differ from the prior art in a first instance in that a single large and wide spring is utilized to develop compressive force for the electrical connection of many conductors, as opposed to having each conductor connected through the force of an individual spring. The prior art of Johnson does not utilize a spring clip, but rather a rigid clip of plastic. This dielectric structure of the Johnson shell allows electrical insultation between the multiple contacted conductors. The present invention shows that if the insulation is stripped only from the substrate contacting side of the flat multiple strip conductor cable at the point of electrical contact, then the clip may be made from spring metal. This greatly simplifies the substrate member, which is essentially unmodified. Finally, the present invention teaches that an improved flexible cable securing force may be derived if the clipping connector utilizes an elastomeric pad to fixedly compress the conductor cable against the substrate body when such connector is seated.